Form of end-measuring bar



Nov. 24, 1925. 1,563,011

- A.J.C.BROOKES FORM 0? END MEASURING BAR Filed July 28. 1924 0. books Patented Nov. 24, 1925.

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FORM OF END-lViEASURING- BAR.

Application filed. July $8, 192%.

Z '0 all to 7mm it may concern Be it known that I, An'rnt n JOHN CI-IAuLns Bnoonns, a subject of the King of Great Britain and Ireland, and residing at Lower Faintree, Bridgnorth, in the county of Salop, England, have invented a certain new and useful Improved Form of End- Measuring Bars, of which the following is a specification.

This invention relates to improvements in the form of end measuring bars of high accuracy.

The finished measuring bars may have the measuring faces truly flat and parallel when they are supported in two certain posi tions; one when the bars are supported in any manner in a truly vertical position and the other when the bars are supported in a horizontal or inclined position in a particu lar manner upon two rigid supports Referring to the horizontal supporting position in practical use of the measuring bars, it is necessary to support them upon two (or more) rigid supports, two supports being now commonly employed when the bars have lengths exceeding about 5 inches and when they are of conveniently small diameter it is found that they sag downwards, due to the natural gravity action, on either side of each support. This natural sagging will cause the measuring faces or ends of the bars to be out of paraL lel with each other in all positions of the two supports relative to the bars, excepting when the two supports are placed symmetrically about the middle of the bars at a distance apart corresponding to 0.57% of the total length of the bar so supported, it being understood that the bars are of uniform cross-section throughout their length.

It should be observed that it has been common practice, when making comparisons in horizontal measuring machines, to support ordinary measuring bars, of uniform cross-section, upon adjustable supports, the

distance apart of which is adjusted in accordance with a formula proposed by the late Sir George Airy, about the year A. D.

1857, where the distance apart of the supports corresponds to:

Serial No. 728,761.

where L total length of bar of uniform section;

ni number of supports employed;

Z distanee apart of supports.

In the general use of the measuring bars made as described in British specification No. 186,149 of 1922 it is convenient to use them for direct reference of size when supported upon any table or bench, or machine base, the surfaces of which may be uneven and not truly flat, it being the main purpose to use these bars without reference to a measuring machine, and the present invention consists in forming raised collars (hereinafter referred to as nodal bands) that are portions of the bar raised above the general surface of the bar at two points corresponding to points of support, which, when the bars are in a horizontal or ap proximately horizontal position, will cause the measuring faces to remain parallel to each other; it then follows that bars having these two nodal bands correctly placed upon them, and with truly parallel end faces, will maintain the end faces parallel to each other when lying upon any surface with which the nodal bands only are in contact.

The nodal bands may be formed integral with the bars or may be added bands. A convenient width of the bands is about 4-inch, and the band will be effective if raised above the general surface of the bar about 1/20-inch.

In the preferred construction according to the invention raised nodal bands upon end measuring bars of uniform cross-section are placed at two points symmetrically disposed about the middle of the bars and at a distance apart equal to 0.5774 of the length of the bars.

The accompanying drawing illust ates one mode of carrying out the invention.

Figure 1 is a front elevation of a circular cross-section measuring bar;

Figure 2 is an end view of same.

In carrying the invention into effect in one convenient manner the main body of the bar, a, is ground reasonably true and approximately cylindrical and with the nodal bands, b, above the general surface. The nodal bands then remain as two small portions of the bar which can be more easily ground truly cylindrical, of equal diameters and with the common axis normal to the parallel end faces, 0.

The principal advantage or manufacture contained in these raised nodal bands, is that these two short lengths oi? the bar are the only portions which it is necessary to make 01 equal diameters and with a common axis normal to the parallel end measuring faces, thereby greatly tacilitating the test ing of the accuracy of the tinished bars.

Having now described my inventiom what I claim as new and desire to secure by Letters Patent is 1. An end measuring bar with parallel end faces and nodal bands intermediate ot the end t'aces.

An end measuring bar with parallel end faces and two nodal bands intermediate of the end faces and disposed syn'nnctrically about the middle of the bar.

3. An end measuring bar with parallel end faces and two nodal bands intermediate ot the end taces and symmetrically disposed about the middle oi? the bar and at a distance apart such that when the bar is supported on the nodal bands the end taees remain parallel to one another under the bending due to gravity action.

t. An end measuring bar having two nodal. bands intermediate ot the end faces and symmetrically disposed about the middle ol the bar and the centres oi? which are separated by a distance equal to 0.5774 times the length of the bar.

An end n'ieasuring bar having parallel end faces and two nodal bands integral with said bar and intermediate of the end faces.

In testimony whereof I have signed my name to this specification.

ARTHUR JGHN CHARLES EROOKELS. 

